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RFC 1510 - 6.3.2. DES in CBC mode with a CRC-32 checksum (des-cbc-crc)

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### 6.3.2. DES in CBC mode with a CRC-32 checksum (des-cbc-crc)

The des-cbc-crc encryption mode encrypts information under the Data Encryption Standard [11] using the cipher block chaining mode [12]. A CRC-32 checksum (described in ISO 3309 [14]) is applied to the confounder and message sequence (msg-seq) and placed in the cksum field. DES blocks are 8 bytes. As a result, the data to be encrypted (the concatenation of confounder, checksum, and message) must be padded to an 8 byte boundary before encryption. The details of the encryption of this data are identical to those for the des- cbc-md5 encryption mode.

Note that, since the CRC-32 checksum is not collisionproof, an attacker could use a probabilistic chosenplaintext attack to generate a valid message even if a confounder is used [13]. The use of collision-proof checksums is recommended for environments where such attacks represent a significant threat. The use of the CRC-32 as the checksum for ticket or authenticator is no longer mandated as an interoperability requirement for Kerberos Version 5 Specification 1 (See section 9.1 for specific details).

Next: 6.3.3. DES in CBC mode with an MD4 checksum (des-cbc-md4)

Connected: An Internet Encyclopedia
RFC 1510 - 6.3.2. DES in CBC mode with a CRC-32 checksum (des-cbc-crc)